Autosomal-dominant mutations in the gene encoding BMPR2 represent the most common mutation encountered in PAH, since they have been documented in 70–80% of hereditary cases of PAH, and in up to 40% of idiopathic PAH; and reduced BMPR2 expression has even been observed in patients with PAH without mutations in BMPR2 [36,37,38]. The gene discussed is BMPR2; the disease is pulmonary arterial hypertension.